Current rotodynamic multiphase pumps, for example as described in document FR-2,665,224, consist of the succession of several compression stages, typically five to fifteen stages. Each stage is made up of a mobile element, referred to as wheel or impeller, and of a fixed element referred to as straightener. The inlet and the outlet of each element is axial, which, by the nature of this geometry, gives the pumps a preferential working range corresponding to low values of pressure gain per stage in the range of relatively high flow rates. This type of pump is therefore particularly well suited for high-power compression stations. The pressure gain of such pumps can be increased by raising the number of stages or by increasing the rotating speed, which, according to the type of application, may unfortunately lead to machine floor space or reliability problems on industrial sites.
For applications corresponding to low flow rates and high pressure gains, the most commonly used concept for compressing mixtures of gas and liquid is the double-screw type positive-displacement pump. This technology however requires relatively frequent mechanical maintenance operations that may limit its use on isolated or hard-to-get-to sites such the ocean depths or oil wells.
The present invention provides a rotodynamic multiphase pump that notably allows compression of mixtures of gas and liquids in a working range that was previously reserved for pumps of double-screw or progressive-cavity (Moineau pumps) type, while escaping the problems inherent in positive-displacement pumps. The device according to the invention is a pump that can be a multistage pump whose mobile wheels comprise a limited number of blades and have a quasi-axial inlet and a semi-radial outlet.